97 lines
3.7 KiB
Go
97 lines
3.7 KiB
Go
package scheduler
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import (
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"fmt"
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"log"
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"github.com/hashicorp/go-memdb"
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"github.com/hashicorp/nomad/nomad/structs"
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)
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// BuiltinSchedulers contains the built in registered schedulers
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// which are available
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var BuiltinSchedulers = map[string]Factory{
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"service": NewServiceScheduler,
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"batch": NewBatchScheduler,
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"system": NewSystemScheduler,
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}
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// NewScheduler is used to instantiate and return a new scheduler
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// given the scheduler name, initial state, and planner.
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func NewScheduler(name string, logger *log.Logger, state State, planner Planner) (Scheduler, error) {
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// Lookup the factory function
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factory, ok := BuiltinSchedulers[name]
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if !ok {
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return nil, fmt.Errorf("unknown scheduler '%s'", name)
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}
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// Instantiate the scheduler
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sched := factory(logger, state, planner)
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return sched, nil
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}
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// Factory is used to instantiate a new Scheduler
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type Factory func(*log.Logger, State, Planner) Scheduler
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// Scheduler is the top level instance for a scheduler. A scheduler is
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// meant to only encapsulate business logic, pushing the various plumbing
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// into Nomad itself. They are invoked to process a single evaluation at
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// a time. The evaluation may result in task allocations which are computed
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// optimistically, as there are many concurrent evaluations being processed.
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// The task allocations are submitted as a plan, and the current leader will
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// coordinate the commmits to prevent oversubscription or improper allocations
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// based on stale state.
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type Scheduler interface {
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// Process is used to handle a new evaluation. The scheduler is free to
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// apply any logic necessary to make the task placements. The state and
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// planner will be provided prior to any invocations of process.
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Process(*structs.Evaluation) error
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}
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// State is an immutable view of the global state. This allows schedulers
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// to make intelligent decisions based on allocations of other schedulers
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// and to enforce complex constraints that require more information than
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// is available to a local state scheduler.
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type State interface {
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// Nodes returns an iterator over all the nodes.
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// The type of each result is *structs.Node
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Nodes() (memdb.ResultIterator, error)
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// AllocsByJob returns the allocations by JobID
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AllocsByJob(jobID string) ([]*structs.Allocation, error)
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// AllocsByNode returns all the allocations by node
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AllocsByNode(node string) ([]*structs.Allocation, error)
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// AllocsByNodeTerminal returns all the allocations by node filtering by terminal status
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AllocsByNodeTerminal(node string, terminal bool) ([]*structs.Allocation, error)
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// GetNodeByID is used to lookup a node by ID
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NodeByID(nodeID string) (*structs.Node, error)
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// GetJobByID is used to lookup a job by ID
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JobByID(id string) (*structs.Job, error)
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}
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// Planner interface is used to submit a task allocation plan.
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type Planner interface {
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// SubmitPlan is used to submit a plan for consideration.
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// This will return a PlanResult or an error. It is possible
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// that this will result in a state refresh as well.
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SubmitPlan(*structs.Plan) (*structs.PlanResult, State, error)
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// UpdateEval is used to update an evaluation. This should update
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// a copy of the input evaluation since that should be immutable.
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UpdateEval(*structs.Evaluation) error
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// CreateEval is used to create an evaluation. This should set the
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// PreviousEval to that of the current evaluation.
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CreateEval(*structs.Evaluation) error
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// ReblockEval takes a blocked evaluation and re-inserts it into the blocked
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// evaluation tracker. This update occurs only in-memory on the leader. The
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// evaluation must exist in a blocked state prior to this being called such
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// that on leader changes, the evaluation will be reblocked properly.
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ReblockEval(*structs.Evaluation) error
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}
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